This is a study of the signal transmission properties of the neural network in the cat retina. Action potentials are recorded extracellularly from single retinal ganglion cells during different stimulus conditions. Stimuli which cause the retinal illumination to vary with time, and stimuli that result in variations of the retinal illumination with distance, as well as moving stimulus targets, have been employed. One of the goals has been to find methods of stimulation which enable us to elicit responses generated by one of the response mechanisms only; to study properties of each mechanism in isolation and to investigate the manner in which the pure central and the pure surround inputs interact at the ganglion cell. In particular we have studied gain changes and spatial summation of adaptive effects within each individual mechanism, rod-cone interaction, bleaching adaptation, visual optics of the cat and correlation between retinal oxygenation and ganglion cell discharge patterns. Only units of concentric center-surround organization have been studied.